Photosensitive integrated circuits such as image sensors and color filters play an important role in capturing images in optical electronic devices. These integrated circuits have been found in consumer electronics products and portable devices such as digital cameras, digital camcorders, and cellular phones. The basics of a complementary metal oxide semiconductor (CMOS) image sensor involves light being filtered by color filters, passing through passivation stacks, metal layers, metal contact holes, dielectric layers, and accepted through photodiodes. The photodiodes then transform the light energy into electrical signals.
Quantum efficiency is one of the factors in determining the photonic performance of photosensitive integrated circuits. The more light a photodiode can collect, the higher is its quantum efficiency, and therefore the better the device performance. One of the ways of boosting quantum efficiency is to add microlenses to collect light energy and to focus that light energy onto the underlying photodiodes.